Since magnetic screws are driven by non-contact coupling using a magnetic force, application of an overload easily tends to cause a synchronization loss between a male magnetic screw and a female magnetic screw. When a synchronization loss is caused in magnetic screws in which a male magnetic screw is rotationally driven, a deviation occurs in coupling between a rotation command for the male magnetic screw and the actual movement position of a female magnetic screw that is a nut and synchronous driving may be disabled. In this case, a positioning failure or an overrun of the nut may be caused. Therefore, it is preferable to predict or detect a synchronization loss when using magnetic screws. PTL 1 discloses a device that detects changes in a magnetic flux due to a synchronization loss by installing a magnetic sensor on a nut.